Traffic Calming Liability Issues - Institute of Transportation Engineers

another, or to design measures for one speed versus another, is discretionary. The duty to warn
motorists of traffic calming measures that require slowing down, or to maintain measures in a safe
condition, or to construct measures per design specifications, is ministerial.
Discretion in the Choice of Measures—Portland
Under sovereign immunity, courts will not second-guess discretionary decisions of public officials
if there is any reasonable basis for them. 6 A recent case out of Portland is most germane. A young
woman died in a collision on a street that was traffic calmed farther down, but not at the accident
location. While complicated by drinking and reckless driving, and by the question of whether the
exact measures approved by the city council had been installed, the central issue was whether the city
had done enough to prevent collisions of this type. The plaintiffs claimed that a diverter should have
been used on this particular street to prevent the teenage practice of "hill jumping." Instead,
following its standard planning process, the city had installed a traffic island and a couple of traffic
circles many years before. The neighborhood had specifically considered and rejected a diverter.
A jury found in favor of the city. The verdict is presently under appeal.
One Inherently Dangerous Device—Speed Bumps
There is an exception to government discretion in the choice of traffic calming measures. One
physical measure has been found by some courts to be patently unsafe when applied to public streets.
It is the speed bump, as opposed to the longer speed hump. 7 Speed bumps are abrupt features that
rise and fall 3 to 4 inches over a span of 1 to 3 feet. Bumps have comfortable crossing speeds of 5
mph or less, which relegates them to parking lots and private driveways as opposed to public
roadways with their higher posted speed limits. 8 In Vickburg v. Harrellton, a landmark case , the
Mississippi Supreme Court ruled that speed bumps constituted an inherent danger to motorists. The
Connecticut courts reached the same conclusion, though with a different reason for declaring them
a public nuisance: their low design speeds could so delay emergency vehicles as to cause serious
injury or loss of life. 9 While an occasional speed bump is still found on a public road, jurisdictions
using this measure are asking for legal
problems.
Bump Profile vs. Hump Profile
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